Investigation of gaseous metabolites from moulds by Ion Mobility Spectrometry (IMS) and Gas Chromatography-Mass Spectrometry (GC-MS)

The metabolism of moulds results in the formation of various microbial volatile organic compounds (MVOCs). These substances can be used as an indicator for the presence of moulds in the indoor environment. Three different mould strains were cultivated on culture media and IMS spectra of gaseous mould metabolites were recorded using a portable mini system with a tritium source and a 5 cm drift cell. The headspace spectra are characteristic for mould species and their age. Typical gaseous components of the metabolites were identified and compared with results obtained from gas chromatography using a mass spectrometer detector. It was observed that the MVOCs formation depends on mould species and their growing stage with a maximum of MVOCs emission occurring during the first 10 days. These preliminary results show that IMS can be applied to detect MVOCs in indoor environment and indicate hidden mould growth.     

Immobilization of Modified Papain with Anhydride Groups on Activated Cotton Fabric

Papain (EC 3.4.22.2) has been chemically modified using two novel reagents including different anhydrides of 1,2,4-benzenetricarboxylic and pyromellitic acids. Then, the modified papain was immobilized on the activated cotton fabric by a two-step method. The number of free amino groups in the modified protein was investigated through the 2,4,6-trinitrobenzenesulfonic acid method. Energy dispersive spectrometer was used to characterize papain immobilization. Some parameters of both modified and native papain immobilized on cotton fabric, such as optimum temperature, optimum pH, and the stabilities for reservation in various detergents were studied and compared. The resultant papain had its optimum pH shifted from 6.0 to 9.0. Compared with immobilized native papain, the thermal stability and the resistance to alkali and washing detergent of immobilized modified enzyme were improved considerably. When the concentration of detergent was 20 mg/ml, the activity of the immobilized pyromellitic papain retained about 40% of its original activity, whereas the native papain was almost inhibited. This work demonstrated that the cotton fabric immobilized modified papain has potential applications in the functional textiles field.     

Hollow fiber supported liquid membrane extraction for ultrasensitive determination of trace lead by portable tungsten coil electrothermal atomic absorption spectrometry

Hollow fiber supported liquid membrane extraction (HF-SLME) was used to separate and enrich trace lead from a large volume of 250 mL water sample to a final tiny volume of 30 μL of 1-octanol, 5 μL of which was inject into a tungsten coil electrothermal atomic absorption spectrometer (W-coil ET-AAS) for determination of lead. Some important parameters that influenced the extraction and determination were investigated in detail, such as the concentration of ammonium pyrrolidine dithiocarbamate (APDC), pH of sample solution, stirring rate, extraction time, pyrolysis current, atomization current, carrier gas flow rate, as well as interferences. Under the optimized conditions, a practical enrichment factor of 499 and a limit of detection (3σ) of 0.2 ng mL^{− 1} were obtained. The calibration curve was linear in the range of 0.5–10 ng mL^{− 1}. The relative standard deviation (RSD) was 5.6% for five measurements of a 4 ng mL^{− 1} lead standard solution. The accuracy of this method was examined by the analysis of certified reference water samples (GBW(E)080398 and GSBZ(E) 50009-88) for lead. Finally, the proposed method was applied to the determination of lead in local tap water, pond water and river water, with recoveries in the range of 96–109% for spiked samples.     

Complex Polypropionates from a South China Sea Photosynthetic Mollusk: Isolation and Biomimetic Synthesis Highlighting Novel Rearrangements

Placobranchus ocellatus is well known to produce diverse and complex γ‐pyrone polypropionates. In this study, the chemical investigation of P. ocellatus from the South China Sea led to the discovery and identification of ocellatusones A–D, a series of racemic non‐γ‐pyrone polyketides with novel skeletons, characterized by a bicyclo[3.2.1]octane ( 1 , 2 ), a bicyclo[3.3.1]nonane ( 3 ) or a mesitylene‐substituted dimethylfuran‐3(2H)‐one core ( 4 ). Extensive spectroscopic analysis, quantum chemical computation, chemical synthesis, and/or X‐ray diffraction analysis were used to determine the structure and absolute configuration of the new compounds, including each enantiomer of racemic compounds 1 – 4 after chiral HPLC resolution. An array of new and diversity‐generating rearrangements is proposed to explain the biosynthesis of these unusual compounds based on careful structural analysis and comparison with six known co‐occurring γ‐pyrones ( 5 – 10 ). Furthermore, the successful biomimetic semisynthesis of ocellatusone A ( 1 ) confirmed the proposed rearrangement through an unprecedented acid induced cascade reaction.     

Cu Nanoparticles Embedded in N‐Doped Carbon Materials for Oxygen Reduction Reaction

Development of eco‐friendly, cost‐effective, and high‐performance electrocatalysts to replace precious metal platinum for oxygen reduction reaction (ORR) has received increasing attention. Herein, we adopt a facile one‐pot strategy to embed Cu nanoparticles onto N‐doped carbon‐graphene (Cu@NC‐700). The Cu@NC‐700 exhibits robust and efficient ORR catalysis with positive half‐wave potential (~0.86 V vs. RHE) and low Tafel slope (33.9 mV?dec^–1) in 0.1 M KOH solution. Meanwhile, it manifests remarkable electrochemical stability, and strong tolerance to methanol crossover and carbon monoxide poisoning. The synergistic effect between Cu‐N‐C sites, Cu nanoparticles, and N‐doped carbon support speeds up ORR electrocatalysis.     

The Effects of Trivalent Lanthanide Cationization on the Electron Transfer Dissociation of Acidic Fibrinopeptide B and its Analogs

Electrospray ionization (ESI) on mixtures of acidic fibrinopeptide B and two peptide analogs with trivalent lanthanide salts generates [M + Met + H]⁴⁺, [M + Met]³⁺, and [M + Met –H]²⁺, where M = peptide and Met = metal (except radioactive promethium). These ions undergo extensive and highly efficient electron transfer dissociation (ETD) to form metallated and non-metallated c- and z-ions. All metal adducted product ions contain at least two acidic sites, which suggest attachment of the lanthanide cation at the side chains of one or more acidic residues. The three peptides undergo similar fragmentation. ETD on [M + Met + H]⁴⁺ leads to cleavage at every residue; the presence of both a metal ion and an extra proton is very effective in promoting sequence-informative fragmentation. Backbone dissociation of [M + Met]³⁺ is also extensive, although cleavage does not always occur between adjacent glutamic acid residues. For [M + Met – H ]²⁺, a more limited range of product ions form. All lanthanide metal peptide complexes display similar fragmentation except for europium (Eu). ETD on [M + Eu – H]²⁺ and [M + Eu]³⁺ yields a limited amount of peptide backbone cleavage; however, [M + Eu + H]⁴⁺ dissociates extensively with cleavage at every residue. With the exception of the results for Eu(III), metallated peptide ion formation by ESI, ETD fragmentation efficiencies, and product ion formation are unaffected by the identity of the lanthanide cation. Adduction with trivalent lanthanide metal ions is a promising tool for sequence analysis of acidic peptides by ETD.

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21 Tesla Fourier Transform Ion Cyclotron Resonance Mass Spectrometer Greatly Expands Mass Spectrometry Toolbox

We provide the initial performance evaluation of a 21 Tesla Fourier transform ion cyclotron resonance mass spectrometer operating at the Environmental Molecular Sciences Laboratory at the Pacific Northwest National Laboratory. The spectrometer constructed for the 21T system employs a commercial dual linear ion trap mass spectrometer coupled to a FTICR spectrometer designed and built in-house. Performance gains from moving to higher magnetic field strength are exemplified by the measurement of peptide isotopic fine structure, complex natural organic matter mixtures, and large proteins. Accurate determination of isotopic fine structure was demonstrated for doubly charged Substance P with minimal spectral averaging, and 8158 molecular formulas assigned to Suwannee River Fulvic Acid standard with root-mean-square (RMS) error of 10 ppb. We also demonstrated superior performance for intact proteins; namely, broadband isotopic resolution of the entire charge state distribution of apo-transferrin (78 kDa) and facile isotopic resolution of monoclonal antibody under a variety of acquisition parameters (e.g., 6 s time-domains with absorption mode processing yielded resolution of approximately 1 M at m/z?=?2700).

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H<Subscript>3</Subscript>PW<Subscript>12</Subscript>O<Subscript>40</Subscript>-catalyzed one-pot synthesis of <Emphasis Type="Italic">bis</Emphasis>(indole) derivatives under silent and ultrasonic irradiation conditions in aqueous media

A convenient and direct approach has been developed for the preparation of bis(indole) derivatives by one-pot four-component condensing of indole, aldehydes and active methylene compounds in the presence of 12-tungstophosphoric acid in aqueous media under silent and ultrasound methods. The remarkable advantages are the simplicity of the experimental procedures, short reaction times and high yields with the green aspects by avoiding toxic catalysts and solvents.     

Recent advances in the application of nanomaterials in enzymatic glucose sensors

Due to the critical role of glucose level in the diagnosis and treatment of diabetes, as well as the increasing number of diabetics, there is an overwhelming demand for developing glucose sensors. It is well acknowledged that these sensors, especially those based on glucose oxidase, have played an important role in blood glucose detection. Inspired by the attractive properties, nanomaterials, especially nanostructured carbon and metal/metal oxides, have been extensively explored to develop enzymatic glucose sensors with high sensitivity, fast response time, and satisfied stability. In this review, a brief history of glucose biosensors is firstly presented. Furthermore, we discuss the currently available fabrication possesses in the field of enzymatic glucose biosensors based on nanomaterials, focusing on the carbon-based, metal-based, and metal oxides-based nanocomposites. What is more, we discuss the challenges and attempt to give an outlook on the possible further developments.     

Kinetics and Mechanism of Cr(VI) Reduction in a Water Cathode Induced by Atmospheric Pressure DC Discharge in Air

The process of reduction of Cr⁶⁺ ions (solution of potassium dichromate, K₂Cr₂O₇) in a water cathode was studied during a DC discharge in air. The concentration range of Cr⁶⁺ was (5.7–19) ×10^?5 mol/l and discharge current range was 20–80 mA. Cr⁶⁺ ions were shown to be reversibly reduced under a discharge action. The equilibrium degree of reduction increased with increasing initial concentration of the solution at fixed discharge current. At fixed initial concentration the reduction degree increased with increasing discharge current. The reduction degrees so obtained were 0.34–0.84. A kinetic scheme of the processes taking place in a solution was proposed. The calculated data obtained as a result of application of this scheme described well the experimental results on Cr⁶⁺ kinetics. The main processes of Cr⁶⁺ reduction and Cr³⁺ oxidation were revealed. HO ₂ ^· radicals and hydrogen peroxide were shown to be responsible for Cr⁶⁺ reduction whereas ^·OH radicals and O₂ molecules provide the reverse process of Cr³⁺ oxidation to Cr⁶⁺. The mechanism of action of phenol additives improving the process efficiency is discussed. The efficiency of phenol action as a radical scavenger was shown to be determined with its mass-transfer to the reaction area rather than chemical reaction rate.